Stabilized formulation

ABSTRACT

A stabilized pharmaceutical composition of anticancer drug and a solvent like Polyethoxylated castor oil (cremophor) also containing any other suitable solubilizer suitable for human administration like dehydrated alcohol, is disclosed. Compositions prepared using this purified polyethoxylated castor oil enhance the stability of paclitaxel in such compositions.

The present invention relates to a stabilized pharmaceutical compositionin a solvent system and in particular a co-solvent system suitable forpreparing a stabilized injection composition containing at least onepharmaceutical agent. More particularly, the present invention relatesto stabilized compositions of anti cancer drugs.

Administration of pharmaceutical compounds, particularly by injection,usually requires a suitable solvent or delivery system to enable thecomposition to be administered to a patient.

An ideal solvent must typically have the following properties:

-   -   1. It must be capable of solubilizing a therapeutically        effective amount of the active agent to produce an effective        composition.    -   2. It must be compatible with the active agent.    -   3. It should be safe i.e. it should not cause any toxicity to        the patient.    -   4. It should produce a composition having a good shelf life.

Many solvents while possessing most of the above advantageous qualitiesare not particularly efficient in solubilizing the pharmaceutical agentto produce an effective composition for administration.

On the other hand numerous pharmaceutical agents are not sufficientlysoluble in any one solvent to enable the resulting composition to beeffective. Therefore, mixtures of two or more solvents are quitecommonly used in pharmaceutical industry to overcome the limitations ofa single solvent to solubilize the active agent. These co-solventsystems are suitable for solubilizing many pharmaceutical agents, whichcannot otherwise be solubilized or dispersed in a single solvent.

One example of a co-solvent system is a mixture of a polar solvent and anon-ionic solvent, such as a mixture of a polyethylene glycol andCremophor EL or ELP (polyethoxylated castor oil). Cremophor EL or ELP isa condensation product of castor oil and ethylene oxide sold by BASF.

Although these co-solvent systems can be effective in solubilizing manycompounds, they are not without their disadvantages. A commonly usedco-solvent system used for many pharmaceutical agents is a 50:50 mixtureof ethanol and Cremophor ELP. A potential problem associated with suchsolvents is that acids, salts or other ionic impurities, as well asresidual water in the solvent or solvent system, even if within theacceptable limits, can catalyze the degradation of the pharmaceuticalagent. For example, co-solvents of ethanol and Cremophor are known toresult in particulates forming upon dilution with infusion solutions. Inaddition, fibrous precipitates of unknown composition form in someformulations during storage for extended periods of time.

A solvent with sufficiently low levels of particularly deleteriousimpurities will yield more stable pharmaceutical compositions. The USFDA approved pharmaceutical composition of Taxol marketed by BristolMyers Squibb is paclitaxel in a co-solvent of 50:50 by volume ofdehydrated ethanol and commercial grade Cremophor EL. These compositionsexhibit a loss of potency of greater than 60% after storage for 12 weeksat 500 C (U.S. Pat. No. 5,504,102). The loss of potency is attributed tothe decomposition of paclitaxel during storage. It is believed thatcarboxylate anions present in Cremophor EL can catalyze thedecomposition of paclitaxel, even at levels within the defined limitsset forth in the National Formulary. U.S. Pat. No. 5,504,102 (Agharkaret al) incorporated herein by reference discloses removing thecarboxylate anions from polyethoxylated castor oils (cremophor) by acidaddition or alumina adsorption. U.S. Pat. No. 5,504,102 discloses thatpaclitaxel reacts with ethanol during storage and that the decompositionof paclitaxel is catalyzed by the carboxylate anions in the solvent.They also disclose that lowering the carboxylate concentration of thesolvent produced a stabilizing effect on the pharmaceutical composition.The composition in question being Taxol, prepared as an injectionconcentrate containing 6 mg/ml paclitaxel in 50:50 by volume ethanol andpolyoxyethylated castor oil.

As per their disclosure, the pharmaceutical agents of interest are thosehaving an ester linkage that can be cleaved by an alcohol in thepresence of carboxylate anions. In their preferred embodiments, thesolvent is a co-solvent mixture of at least one solvent and asolubilizing agent. The preferred solvent includes alcohol such asdehydrated ethanol. The solubilizing agent in preferred embodiments is apolyoxyethylated castor oil such as that sold under the tradenameCremophor EL or Cremophor ELP by BASF.

In their preferred embodiments, the carboxylate anion content of thesolvent is lowered by a number of methods. In one embodiment of theinvention, the Cremophor EL or other solvent is passed through astandard chromatography column of aluminum oxide which adsorbs thecarboxylate anions as well as other impurities to reduce the carboxylateanion content of the solvent. In an alternative embodiment, the solventis treated by the addition of an acid in a stabilizing amount to reducethe carboxylate anion content to a sufficiently low level tosubstantially prevent catalyzed degradation of the pharmaceuticalcompound.

Nikolayev et al in U.S. Pat. No. 5,925,776 disclose a method of reducingthe cation content in the polyethoxylated castor oil (cremophor). Thisis achieved by pre-treating the polyethoxylated castor oil with a strongcation exchange resin. The low cationic content polyethoxylated castoroil of the invention is then utilized to prepare formulations of variousagents which are found to be sensitive to the previously commerciallyavailable polyethoxylated castor oil (cremophor EL). The stability ofpaclitaxel formulated in a mixture of low cationic contentpolyethoxylated castor oil of the invention and ethyl alcohol is shownto be better as compared to a formulation using untreatedpolyethoxylated castor oil of the invention and ethyl alcohol.

Anevski et al in U.S. Pat. No. 6,388,112 disclose a process forpurifying a non-ionic surfactant or solvent capable of dispersing andsolubilizing a pharmaceutical compound. In the process, a solution ofsolvent and alcohol is brought in contact with an activated carboncolumn and an ion exchange resin column. The process is particularlyadapted to the purification of polyethoxylated castor oils. The purifiedsolvent is useful in the preparation of pharmaceutical compositionshaving enhanced shelf life, such as for use with paclitaxel.

Carver et al in U.S. Pat. No. 6,306,894 disclose a pharmaceuticalformulation of paclitaxel and polyethoxylated castor oil wherein theformulation is relatively acidified to a pH of less than 8.1 andpreferably within a pH range of 5 to 7, inclusively. Ethanol isoptionally included in the formulation. A formulation method is alsodisclosed and includes the step of mixing an acid with a carriermaterial, such as polyethoxylated castor oil, to form a carrier solutionafter which paclitaxel is added in an amount such that the resulting pHis less than 8.1 and preferably in a pH range of 5 to 7. Ethanol mayoptionally be slurried with the paclitaxel before mixing with thecarrier solution.

A variety of acidifying agents, a preferred one being anhydrous citricacid, are described. Acids in the form of powders, for example citricacid, have been preferred over those which contain water, for examplesulfuric acid. The most preferred acid for use in accordance with theinvention disclosed in U.S. Pat. No. 6,306,894 is citric acid, but awide range of acids may be used including:

Citric acid-monohydrous, Citric acid-anhydrous, Citric acid-hydrous,Acetic acid, Formic acid, Ascorbic acid, Aspartic acid, Benzenesulphonic acid, Benzoic acid, Hydrochloric acid, Sulphuric acid,Phosphoric acid, Nitric acid, Tartaric acid, Diatrizoic acid, Glutamicacid, Lactic acid, Maleic acid, and Succinic acid.

Owens et al in U.S. Pat. No. 6,071,952 disclose a pharmaceuticalcomposition with long term storage stability comprising a taxane ortaxoid by incorporating an effective amount of an antioxidant.

Previous efforts to develop a shelf stable composition of somepharmaceutical compositions in various co-solvent systems have not beenentirely successful. Thus, there is a continuing need in the art for asolvent or co-solvent system capable of being used for preparingstabilized compositions and, in particular, stabilized injectioncompositions containing a pharmaceutical agent.

The disadvantages and limitations of the previous injection compositionand solvent systems are overcome by the present invention whileproviding a convenient and efficient method of producing a solvent and amethod of stabilizing pharmaceutical compositions including compositionssuitable for injection. The present invention is primarily directed to asolvent suitable for producing a stabilized pharmaceutical compositionand to a method of producing and stabilizing a pharmaceuticalcomposition.

The invention is directed to a solvent suitable for preparing stabilizedinjection compositions containing at least one pharmaceutical agent.Accordingly, it is a primary aspect of the invention to provide a methodof preparing a treated solvent which when used in a composition has astabilizing effect on the composition and a method of preparingstabilized pharmaceutical compositions using the treated solvent.

The stabilized pharmaceutical compositions produced using the treatedsolvent of the invention have been shown to have a shelf life greaterthan the compositions produced from untreated solvent. The solventsystem of the invention is particularly suitable for use withpharmaceutical compounds that exhibit decomposition, which is catalyzedby the presence of ionic, metallic and oxidizing impurities. Theadvantages of the invention are also attained by producing a stabilizedpharmaceutical composition comprising at least one antineoplasticcompound and a solvent system capable of solubilising the antineoplasticcompound, the solvent system comprising a solubilizing amount of analcohol such as absolute alcohol and a solubilizer such aspolyoxyethylated castor oil having been purified to have an impuritiescontent sufficiently low to substantially minimize degradation of theantineoplastic compound.

Of particular interest are the antineoplastic agents such as paclitaxel,teniposide, camptothecin and derivatives thereof.

DETAILED DESCRIPTION OF THE INVENTION

The solvent system of the invention essentially comprises a purifiednon-ionic solvent The solubilizing agent can be a condensation productof an alkylene oxide and a lipid or fatty acid. The preferredsolubilizing agent includes a polyoxyethylated castor oil such as thatsold by M/s BASF under the tradename Cremophor EL or Cremophor ELP andan alcohol. The polyoxyethylated castor oil is purified by a process ofchromatography to reduce the water soluble ionic, metallic and oxidizingimpurities to a sufficiently low concentration to minimize thedecomposition of the pharmaceutical agent that is catalyzed by thepresence of these impurities. The content of impurities in thepolyoxyethylated castor oil is lowered by reverse-phase chromatographyusing suitable mobile and stationary phases.

Further advantages of the invention are attained by providing a methodof stabilizing a pharmaceutical composition containing a pharmaceuticalagent such as paclitaxel, teniposide, camptothecin and derivativesthereof, and a solvent containing absolute ethanol and a purifiedsolubilizing agent as described above.

The invention provides a pharmaceutical stable formulation of paclitaxelmade using a purified solvent. The process involves purification of anon-ionic solvent such as polyethoxylated castor oil, preferablypolyoxy-35-castor oil, more preferably cremophor such as Cremophor EL orCremophor ELP using reverse-phase chromatography such that the contentof ionic, metallic and oxidizing impurities of the cremophor is lowered.

The process for purifying a non-ionic solvent comprising the steps of:

-   -   (a) forming a solution of the non-ionic solvent in alcohol and        water, with or without the aid of heating;    -   (b) loading this solution on to a chromatography column packed        with reverse phase silica    -   (c) running the chromatograph using de-ionized water as the        mobile phase to purify the solvent;    -   (d) running the chromatograph using an eluent to recover the        purified solvent; and    -   (e) evaporating the residual water and the eluent.

Preferably the de-ionized water is HPLC grade.

The aqueous fractions obtained from running the chromatograph usingde-ionized water are not used and may be set aside or discarded.

Preferably, the solvent is selected from polyethoxylated castor oil,polyoxy-35-castor oil, Cremophor EL or Cremophor ELP.

Preferably, the alcohol is selected from methanol, ethanol, butanol,iso-propanol etc; more preferably ethanol and more preferably dehydratedethanol.

The eluents may be selected from methanol, ethanol, isopropyl alcohol,acetone, acetonitrile, tetrahydrofuran and other such solvents ofsimilar polarities. The preferred eluent is acetone. Combinations ofeluents may be used.

In one embodiment of the invention the mobile phase is run for 1 to 50minutes; preferably for 20 minutes.

In one of the preferred embodiments of the invention, thepolyethoxylated castor oil is purified by loading it on a chromatographycolumn packed with reverse-phase silica, preferably C-8 or C-18 andchromatographed using de-ionized water to remove or lower theconcentration of water soluble impurities - both organic and inorganic.The purified polyethoxylated castor oil is then recovered by eluting thecolumn using an eluent, preferably acetone. Preferably the de-ionizedwater is HPLC grade.

In a preferred embodiment the weight ratio of polyethoxylated castor oilto alcohol is 10:1. In another embodiment of the invention the ratio ofpolyethoxylated castor oil to alcohol to water is 10:1:33 w/v/v.

The solvent purified by this method can be combined with antineoplasticcompound to form a composition. Optionally the compositions of thisinvention include an alcohol which may be added to the solvent beforecombining with the antineoplastic agent,t when the solvent is combinedwith the antineoplastic agent or after the solvent is combined with theantineoplastic agent. The alcohol may be a dehydrated alcohol.Compositions suitable for parenteral administration such as injection orinfusion may be prepared by diluting the compositions with a suitableparenteral fluid prior to parenteral administration, injection orinfusion.

The following non-limiting example is intended to demonstrate thepreferred embodiment of the invention. One skilled in the art willreadily recognize that numerous embodiments of the invention can bepracticed to achieve the stabilizing effect.

EXAMPLE-1

This example was carried out to demonstrate the effect of purificationof cremophor using reverse phase chromatography on the stability ofPaclitaxel formulation.

300 gm of Cremophor ELP (of M/s BASF) was diluted with about 30 ml ofabsolute ethanol and the mixture was then dissolved in one litre of HPLCgrade de-ionized water pre-heated to 60° C. with stirring to makeuniform solution.

This cremophor solution was then loaded on to a chromatography column(15 cm×30 cm) packed with reverse-phase silica, preferably C-8 or C-18,having an average particle size of 30 to 60 μ. The system was elutedusing de-ionized HPLC grade water as the mobile phase for about 20minutes to remove or reduce the water-soluble impurities in thecremophor. The eluted aqueous fractions were discarded. The column wasthen eluted with 100% acetone to recover the purified cremophor. Acetonewas completely removed by evaporation under vacuum using rotavapor at40° C. The so obtained cremophor was further dried under vacuum atelevated temperature of about 55° C. to remove the residual water toobtain purified cremophor.

The purified cremophor so obtained was tested for various impuritiesincluding anions and cations. The cation and anion content was measuredin the cremophor before and after purification and the results are asbelow

Cation Content: Identity Zinc Magnesium Sodium Potassium Aluminum TinCalcium Cremophor 2.93 7.86 28.67 3.00 0.78 1.28 32.62 ELP (BASF)ELP-Prep 1 2.10 5.99 31.39 3.36 0.33 0.78 22.25 ELP-Prep 2 1.89 4.6031.52 3.48 0.37 0.32 17.83 ELP-Prep 3 1.58 4.60 32.12 3.39 0.13 0.3318.89All values are in ppm

As is evident from the above table there is substantial decrease in theconcentrations of most of the cations listed above except sodium andpotassium. All the above tabulated cations are known to promotedegradation of paclitaxel.

Anion Content: Identity Chloride Bromide Sulphate Cremophor 23.211 0.6576.747 ELP (BASF) ELP-Prep 1  4.625 ND 2.545 ELP-Prep 2 14.673 ND 6.014ELP-Prep 3 15.386 ND 2.352All values are in ppm;ND = Not detectable

As is evident from the above table there is a decrease in theconcentrations of the inorganic anions, as compared to the untreatedCremophor ELP from M's BASF. These purified cremophor samples were thenused to make formulations of paclitaxel and subjected to stresstemperature studies to see the effect on formation of degradationproducts of paclitaxel.

Samples 1 to 3 were prepared by dissolving 6 mg/ml of paclitaxel in50:50 v/v mixture of purified cremophor ELP and absolute ethanol. TheCremophor ELP of the samples 1 to 3 was purified as discussed above.Sample 4 was prepared as a control sample from unprocessed Cremophor ELPin a 50:50 v/v mixture of unprocessed Cremophor ELP and ethanol withpaclitaxel in the amount of 6 mg/ml.

The samples were then subjected to a stress temperature study at 50° C.The results obtained are summarized as below: TABLE 1 PaclitaxelDegradation Products % at 50° C. PH Total (including other (1:10dilution in water) degradation products) Cremophor Formulation 3 Days 10Days 30 Days Sample 1 5.02 5.04 0.07 0.14 0.24 Sample 2 5.03 5.08 0.090.16 0.28 Sample 3 5.10 5.12 0.09 0.13 0.23 Sample 4 5.70 5.71 0.62 1.291.79

The degradation products of paclitaxel include: Baccatin III, EthylEster Side Chain of Paclitaxel, 10-Deacetyl Paclitaxel,10-Deacetyl-7-Epi-paclitaxel, and 7 Epi-paclitaxel.

As is evident from the above results, purification of cremophor resultsin reduction of the pH of cremophor from about 5.70 to around 5.10. Asshown in Table 1—Samples 1 to 3 prepared with purified cremophor aremuch more stable in terms of degradation products of paclitaxel ascompared to sample—4. Thus, cremophor ELP purified using the process ofthe invention improves the stability of paclitaxel formulationsignificantly as compared to the formulation made using untreatedCremophor ELP.

The foregoing description of the preferred embodiment of the inventionhas been presented for purpose of illustration and description. It isnot intended to be exhaustive or to limit the invention to preciseparameters disclosed. Obvious modifications or variations are possiblein light of the above teachings. The embodiment has been chosen anddescribed to provide the best illustration of the principles of theinvention and its practical applications to thereby enable one of theordinary skill in the art to utilize the invention in variousembodiments and with various modifications like using various sizechromatographic columns, different types of reverse-phasechromatographic materials, column packing materials of differentparticle size, and/or different chromatographic temperatures etc. Allsuch modifications and variations are within the scope of the inventionas determined by the appended claims.

1. A process for purifying a non-ionic solvent comprising the steps of:(a) forming a solution of said solvent in alcohol and water, with orwithout aid of heating; (b) loading the solution on to a chromatographycolumn packed with reverse phase silica (c) running the chromatographycolumn using de-ionized water as the mobile phase to purify the solvent;(d) running the chromatography column using an eluent recovering thepurified solvent; and (e) evaporating the residual water and the eluent.2. The process according to claim 1 wherein the solvent ispolyethoxylated castor oil or polyoxyl-35-castor oil.
 3. The processaccording to claim 1 wherein the solvent is Cremophor EL or CremophorELP.
 4. The process according to claim 1 wherein the alcohol is selectedfrom the group consisting of methanol, ethanol, butanol or isopropanol.5. The process according to claim 1 wherein the alcohol is ethanol. 6.The process according to claim 1 wherein the eluent is selected from thegroup consisting of methanol, ethanol, isopropyl alcohol, acetone,acetonitrile and tetrahydrofuran.
 7. The process according to claim 1wherein the eluent is acetone.
 8. The process according to claim 1wherein the de-ionized water is HPLC grade.
 9. The process according toclaim 1 wherein in step (a) said solution is a solution ofpolyethoxylated castor oil, alcohol and water.
 10. The process accordingto claim 1 wherein said step of forming said solution comprises mixingabout polyethoxylated castor oil, dehydrated ethanol and de-ionizedwater in a ratio of 10:1:33 w/v/v with or without the aid of heat. 11.The process according to claim 1 wherein said step of forming saidsolution comprises mixing about 300 gm of polyethoxylated castor oil, 30gm of dehydrated ethanol and one litre of HPLC grade non ionic waterwith or without the aid of heat.
 12. The process according to claim 1wherein said solvent is polyethoxylated castor oil and the step thechromatography column comprises a column of 15×30 cms packed withreverse phase silica of C-8 or C-18 type having a particle size of30-60.
 13. The process according to claim 1 wherein the step of runningthe chromatograph to purify the solvent comprises the use of de-ionizedwater as the mobile phase for 1 to 50 minutes.
 14. The process accordingto claim 13 wherein the de-ionized water is HPLC grade.
 15. The processaccording to claim 1 wherein the aqueous fractions are discarded.
 16. Acomposition comprising combining the purified non-ionic solvent preparedaccording to the process of claim 1 and paclitaxel.
 17. The compositionaccording to claim 16 wherein the percent by weight of degradationproducts of paclitaxel after being stored at 50° C. for 10 days is lessthan or equal to 0.3% wherein said degradation products are BaccatinImI, Ethyl ester side chain of Paclitaxel, 10-Deacetyl paclitaxel,10-Deacetyl 7-epipaclitaxel and 7-epipaclitaxel.
 18. A process forpurifying a polyoxyl 35 castor oil solution said solution comprisingpolyoxyl 35 castor oil, water and an alcohol said process comprisingloading the solution on to a chromatography column packed with reversephase silica and running the chromatograph using de-ionized water as themobile phase followed by eluting the purified polyoxyl 35 castor oilwith methanol, ethanol or acetone evaporating the residual alcohol,water and methanol, ethanol or acetone to obtain purified polyoxyl 35castor oil adapted to produce, when combined with paclitaxel, apharmaceutical composition not showing more than 0.3% degradationproducts of paclitaxel identified as Baccatin III, Ethyl ester sidechain of Paclitaxel, 10-Deacetyl paclitaxel, 10-Deacetyl 7-epipaclitaxeland 7-epipaclitaxel, after being stored at 50° C. for 10 days.
 19. Aprocess for purifying a polyoxyl 35 castor oil solution said solutioncomprising polyoxyl 35 castor oil, water and an alcohol said processcomprising loading the solution on to a chromatography column packedwith reverse phase silica of C-8 or C-18 type having a particle size of30 - 60 and running the chromatograph using de-ionized water (HPLCgrade) as the mobile phase followed by eluting the purified polyoxyl 35castor oil with methanol, ethanol or acetone, evaporating the residualalcohol, water and methanol, ethanol or acetone to obtain purifiedpolyoxyl 35 castor oil adapted to produce, when combined withpaclitaxel, a pharmaceutical composition not showing more than 0.3%degradation products of paclitaxel identified as Baccatin II, Ethylester side chain of Paclitaxel, 10-Deacetyl paclitaxel, 10-Deacetyl7-epipaclitaxel and 7-epipaclitaxel, after being stored at 50° C. for 10days.
 20. The process according to claim 19 wherein the eluent isacetone.
 21. A pharmaceutical composition comprising a solventcontaining a solvent purified according to the process of claim 1wherein the solvent is a polyethoxylated castor oil and a pharmaceuticalagent.
 22. The composition according to claim 21 wherein thepharmaceutical agent is an antineoplastic agent.
 23. The compositionaccording to claim 22 wherein the pharmaceutical agent is paclitaxel.24. The composition of claim 21 wherein said solvent further comprisesan alcohol.
 25. A stabilized pharmaceutical composition comprising asolvent containing a purified polyethoxylated castor oil according toclaim 19 and paclitaxel, said composition showing not more than 0.3%degradation products of paclitaxel identified as Baccatin III, Ethylester side chain of Paclitaxel, 10-Deacetyl paclitaxel, 10-Deacetyl7-epipaclitaxel and 7-epipaclitaxel, after being stored at 50° C. for 10days.
 26. A pharmaceutical composition comprising a solvent containing asolvent purified according to the process of claim 2 wherein the solventis a polyethoxylated castor oil and a pharmaceutical agent.
 27. Apharmaceutical composition comprising a solvent containing a solventpurified according to the process of claim 3 wherein the solvent is apolyethoxylated castor oil and a pharmaceutical agent.
 28. Apharmaceutical composition comprising a solvent containing a solventpurified according to the process of claim 4 wherein the solvent is apolyethoxylated castor oil and a pharmaceutical agent.
 29. Apharmaceutical composition comprising a solvent containing a solventpurified according to the process of claim 10 wherein the solvent is apolyethoxylated castor oil and a pharmaceutical agent.
 30. Apharmaceutical composition comprising a solvent containing a solventpurified according to the process of claim 11 wherein the solvent is apolyethoxylated castor oil and a pharmaceutical agent.